The present invention relates to a developing apparatus using a liquid developer and applicable to image forming equipment implemented with an electrophotographic, electrostatic or Similar system such as a copier, facsimile apparatus or printer.
One of conventional developing apparatuses of the type described has a developing head which is formed with a groove on the surface thereof facing a medium transport path, as disclosed in, for example, Japanese Patent Laid-Open Publication Nos. 179477/1986 and 185569/1989. The groove extends in the widthwise direction of, for example, an electrophotographic recording medium which is transported along the transport path. The apparatus develops a latent image electrostatically formed on the medium by filling the groove with a liquid developer. While the open end of the groove is closed by the medium, a pump motor or similar vacuum generating means is driven to suck the medium onto the surface of the head. After the development, the supply of the liquid to the groove is stopped, and the liquid in the groove is returned to a reservoir.
However, when the supply of the liquid to the groove is simply interrupted to return the liquid in the groove to the reservoir by gravity, the liquid remains in the form of a meniscus at the corner defined by the upper inner portion of the groove and the medium. As the medium is transported in such a condition, the remaining liquid is transferred from the head to the medium to smear the latter. When the medium is, for example, an electrostatic recording medium, smeared part thereof has to be simply discarded. Assume a color developing apparatus having a plurality of developing heads each being supplied with a liquid developer of particular color and moving particular one of the heads to a developing position where it faces a medium transport path. In such an apparatus, a recording medium is repetitively moved back and forth to opposite sides of the developing position. This brings about a problem that when the head located at the developing position is retracted to a standby position with the liquid remaining at the above-mentioned corner thereof, the liquid is apt to dry and solidify there and, therefore, apt to smear the medium when moved again to the developing position later. The developer deposited on the medium would smear means for transporting the medium. To eliminate this problem, the medium may be transported before the head having developed an image is retracted to the standby position, causing the remaining liquid to deposit on the medium. This, however, not only wastes the medium but also increases the width over which the medium has to be transported and thereby increases the developing time. Moreover, when the transport of the medium is interrupted while the development of a latent image by the developing head is under way due to a jam or similar cause, simply deactivating the vacuum generating means fails to remove all the liquid remaining on the head. This liquid is likely to deposit in a great amount on the medium and to smear the operator's hands and cloths as well as the medium transporting means.